Volume 2, Issue 1 (January 1974)

Dependence of Fatigue Notch Factor on Plasticity and Duration of Crack Growth

The effects of several factors which influence the magnitude and variation with life of fatigue notch factor (Kf) are discussed in this paper. Plasticity at the roots of stress raisers is known to have the most dominant influence on the variation of Kf when a failure criterion of fatigue crack initiation is employed. When a failure criterion other than cycles to crack initiation is employed, the duration of crack propagation becomes a significant factor in the determination of magnitude and variation of Kf. The duration of crack propagation is viewed as a primary influence on the magnitude of Kf since the increase in propagation duration with increasing theoretical stress concentration factor (Kf) accounts in part for the decrease in notch sensitivity. New evidence is given to the influence of the above two factors on Kf and an attempt is made to add to the understanding of fatigue process in notched components.